That does not seem to make a difference for the Light version. I still get the message, "Message automatically saved
Click here to recover the last item you were working on
The item you were working on was automatically saved to the Drafts folder because no action occurred for an extended period of time. You may be required to log on again. "

I set it for 60 minutes. I did reset IIS. It timed out after 5 minutes.

A. By default, when OWA has forms-based authentication enabled, sessions have a 15-minute inactivity timeout for public or shared computers and 24 hours for a private computer. If you're using a public computer to compose a long email message that takes more than 15 minutes to write, the session will time out and you won't be able to send the message. You can change this timeout value (which is the cookie lifetime) by using this procedure:
1. Log on to the Exchange server as an Administrator.
2. Start the registry editor (regedit.exe).
3. Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeWEB\OWA subkey.
4. From the Edit menu, select New - DWORD value.
5. Enter a name of PublicClientTimeout and press Enter.
6. Double-click the new value and set it to the desired number of minutes before a timeout (1 to 4320), set the type to decimal, and click OK.
7. To set the timeout period for a private client, repeat the process of creating a DWORD value, but this time enter a name of TrustedClientTimeout and again set the value to the number of minutes before a timeout (The value for private computers should be significantly higher than for public computers.)
8. Stop and restart the World Wide Web (WWW) Publishing service by using these commands at the command line.

Managing Active Directory can get complicated. Often, the native tools for managing AD are just not up to the task. The largest Active Directory installations in the world have relied on one tool to manage their day-to-day administration tasks: Hyena. Start your trial today.

ok, let do some test, I've just checked that the timeout is above 10mins, but less than 19Mins.
Will narrow the time down a little more before registry change to shorten the period.
It is a cookie timeout, so it will be that time period after last use; each time you change the page, it will reset the timer (from the server, not locally).

The response we got from Dell Gold support who theoretically contacted Microsoft was that it's a feature not a bug, they won't fix anything that is Exchange 2003 backend mailboxes and Exchange 2007 OWA. We confirmed that users we migrate to Exchange 2007 mailboxes work correctly. Problem is we are not ready to migrate all 10,000 users to Exchange 2007 mailboxes.

A couple of months ago we ran into an issue that necessitated re-creating our Edge Subscriptions. However, when we attempted to execute the command: New-EdgeSubscription -filename C:\NewEdgeSub_01.xml we received an error indicating that the LDAP se…

This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online.
The email signature template has been downloaded from:
www.mail-signatures…

A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA).
For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651
If you want to manage em…